It is known in the art, [see M. L. Hallensleben, J. Polymer Science: Symposium No. 47, 1-9 (1974)], that linear and cross-linked copolymers of 4-vinylpyridine borane, 4-vinylpyridine, and styrene can be prepared and used as polymeric reducing agents for aldehydes and ketones. It is also reported in the literature, [see E. Cernia and F. Gaspuarini, J. Applied Polymer Science, vol. 19, 917-20 (1975)], that 4-vinylpyridine borane hydride polymers rapidly decompose in aqueous solutions of strong mineral acids and can only be used as reducing agents for aldehydes and ketones at or about neutral pH.
U.S. Pat. No. 3,928,293 granted Dec. 23, 1975 discloses solid cross-linked thiohydrocarbon borane hydride polymers and their use as reducing agents for aldehydes ketones, lactones, oxides, esters, carboxylic acids, nitriles and olefins. These borane polymers although stabile at room temperature can release borane (BH.sub.3) under conditions of reduced pressure or heat and are disclosed as being useful as a convenient means of storing borane. U.S. Pat. No. 3,609,191 granted Sept. 28, 1971 discloses polyethylene imine borane complexes which are stable toward hydrolysis at a pH as low as 5.0. These compositions are useful as reducing agents in chemical plating baths for nickel, copper and silver in a pH range of 5 to 8. However, these products are viscous or solid polymers which range in water solubility from completely soluble to slightly soluble depending on the ratio of BH.sub.3 to amino groups in the polymer. The use of ion-exchange resins to extract heavy metals from aqueous solutions via ion-exchange mechanisms is also reported in the art.